1. Field of the Invention
The present invention relates to an optical scanning apparatus in which a light beam from a light source is deflected and scans, and in particular, to an optical scanning apparatus in which a light beam impinges upon a deflecting element a plurality of times and a deflection angle accordingly increases, and also to an image forming apparatus which comprises such an optical scanning apparatus.
2. Description of the Related Art
In an attempt to increase a deflection angle, a conventional optical scanning apparatus for use within an image forming apparatus such as a laser beam printer, a copier machine and a facsimile machine in some cases uses a structure that a deflecting element deflects a light beam a plurality of times. For instance, in the optical scanning apparatus described in U.S. Pat. No. 3,771,850, a light beam deflected by a deflection mirror surface of a deflecting element is guided back to the deflection mirror surface once again and the deflection angle of the light beam thus deflected for the second time accordingly increases. The light beam then emitted from the deflecting element is guided upon a surface-to-be-scanned through a scanning lens. The scanning speed of the light beam increases in this manner as the light beam impinges upon the deflecting element a plurality of times.